1. Field of the Invention
The present invention relates to devices, systems and methods for processing images, and particularly to a device, system and method for realizing on screen display (OSD) translucency.
2. Related Art
On screen display (OSD) technology is widely used in image processing devices such as TVs (televisions), PCs (personal computers), and mobile terminals. The OSD displays additional information such as a channel selection and display time of the image processing device.
However, conventional OSD techniques have a shortcoming in that the OSD partially covers images being shown on the screen of the image processing device. Referring to FIG. 5, image (e) schematically illustrates an original image of an image processing device, and image (f) schematically illustrates an OSD image. Image (g) shows the OSD image without a background color. When the OSD image and the original image are combined as shown in image (h), the OSD image partially covers the original image, which can significantly mar the appearance of the original image.
If the OSD image is made translucent, the above-described problem is readily solved. Viewers can see both the OSD image and the original image simultaneously.
A typical system and method for realizing OSD translucency generally adopts alpha blending theory that complies with the RGB (red green blue) standard. The alpha blending theory is a process of combining a foreground RGB color with a background RGB color, and then producing a new blended RGB color. That is, RGB data of the OSD signals and RGB data of the video signals are alpha blended to realize the OSD translucency. Formulas that describe the alpha blending theory are as follows:
  {                                          Blended            -            red                    =                      Foreground            -                          red              *              alpha                        +            Background            -                          red              *                              (                                  1                  -                  alpha                                )                                                                                              Blended            -            green                    =                      Foreground            -                          green              *              alpha                        +            Background            -                          green              *                              (                                  1                  -                  alpha                                )                                                                                              Blended            -            blue                    =                      Foreground            -                          blue              *              alpha                        +            Background            -                          blue              *                              (                                  1                  -                  alpha                                )                                                           wherein alpha is a parameter, and alpha values are in the range from 0 to 1; the RGB data of the OSD signals are respectively represented as foreground-red, foreground-green, and foreground-blue; and the RGB data of the video signals are respectively represented as background-red, background-green, and background-blue. Different translucency effects are realized by selecting different alpha values. However, the alpha blending process needs a multiplication device with a complicated operation.
Further, for many image processing devices, image signals are generally processed or transmitted based on the YUV standard. The YUV (YCrCb) standard is a color encoding standard that is used worldwide as a television broadcasting standard. Y signals stand for a luminance component. U signals and V signals stand for chrominance components. One advantage of the YUV standard is that signals can be easily manipulated to selectively discard some information and thereby reduce transmission bandwidth. However, the above-described conventional method for realizing OSD translucency adopts the alpha blending theory, which is based on the RGB standard. Therefore, in order to utilize the OSD translucency method, video signals and OSD signals that comply with the YUV standard must be changed to signals that comply with the RGB standard. The change can result in image display error.
Therefore, a heretofore unaddressed need exists in the industry to overcome the aforementioned deficiencies and inadequacies.